1. Field of the Invention
This invention relates to air ventilation and purification systems and in particular to a commercial air ventilation system suitable for removing cooking fumes and other waste produced as a result of restaurant or commercial establishment cooking.
2. Background of the Invention
Large restaurants and other commercial cooking establishments employ a kitchen which may have numerous stove tops and ovens all operating simultaneously, cooking food in quantities much larger than is normally encountered in a residential kitchen. As a result of cumulative open stove cooking over a hot grill, large amounts of air may be contaminated with cooking fumes and grease that is normally produced in the cooking process. In order to comply with local municipal codes as well as assuring health, safety and cleanliness of the kitchen facilities, the heated and contaminated air must be evacuated from the kitchen and away from the stove. The Prior Art has taught that a mere exhaust hood is not sufficient to accomplish the requirements of commercial air ventilation.
In particular, U.S. Pat. Nos. 4,085,735 (issued Apr. 25, 1978) and 4,186,727 (issued Feb. 5, 1980), both to Kaufman, are directed to an air ventilation and washing system suitable for use in a commercial establishment and are typical of the conventional commercial exhaust and ventilation art. These references note that if the only focus of cooking were the exhaust, the strength of the exhaust fans needed to clean the air within a commercial kitchen would subject the kitchen facilities to enormous drafts resulting in difficulties as well as intolerable working conditions during the extremes of summer and winter. Such a large "exhaust-only" system does not allow the restaurant or commercial establishment to maintain a reasonable temperature in its kitchen for proper working conditions. In order to remove the grease laden and contaminated air derived from the cooking process in the commercial kitchen from the premises, it is necessary to provide an input of "make-up air" to replace the air being exhausted from a commercial cooking establishment.
In particular, the Kaufman '727 patent is directed to an air ventilation and washing system which provides a commercial hood where make-up air is directed vertically downward into an exhaust chamber which leads directly up an output duct for exhausting contaminated air off the premises. The conventional air ventilation system, represented by the Kaufman '727 patent, is a system which provides ambient make-up air supplied to a make-up air plenum, which is then distributed to the exhaust cavity.
After mixing with room air and contaminated air above the cooking surface, the ambient make-up air from the exterior does not contact the personnel working below the hood or the food or cooking services below the hood. In addition, Kaufman attempts to exhaust the contaminated air while avoiding turbulence and escape of contaminated air from the exhaust collector cavity.
Although such an air ventilation system, as disclosed in Kaufman '727, moves in the direction of proper make-up air distribution for replacing contaminated air, the Kaufman system relies on the creation of a vortex by a vortex baffle provided in the hood between the make-up air cavity and the exhaust cavity to cause the mixing of room air and make-up air from the exterior. The make-up air is first directed vertically downward; and, then the make-up air is expected to sharply turn twice, in a U-turn fashion, whereby air is directed immediately upward and out an exhaust duct.
The Kaufman hood design is directed to a system which allows little mixing of the make-up air with the air immediately above the surface of the stove, but rather causes the make-up air to mix with the contaminated air at a height sufficiently above the stove surface so that make-up air does not contact kitchen personnel.
While the Kaufman '727 patent discloses ambitious goals for achieving proper air ventilation in a commercial kitchen, providing vertically spaced perforated plates and intermediate vertical baffles which cause the air to travel in a tortuous path along the length of the make-air plenums needlessly complicates the ventilation system. In fact, in one environmental plan, FIG. 14 of Kaufman, the make-air from the plenum (after tortuously passing through a make-up air diffuser) is required to pass through a constricted screen 283(a) which is one-third the width of the body along sidewall 291, before the air enters the exhaust chamber. Also the Prior Art as represented by Kaufman places great reliance on the vortex established by baffle 67 where the make-up air 164 mixes with contaminated air 161 (FIG. 4). The Kaufman '727 patent has a combination plate and screen fabric which comprise the air diffusion means. This is an elaborate element and requires precision manufacture and costs. A clamping means is needed to hold these elements of the diffusion means together. Thus, the state of the art heretofore envisions a complex mechanism for air diffusion and vortex creation.